The present invention relates to a portable telephone apparatus, and particularly to a portable telephone apparatus of a mobile communication system, in which a frequency transmitted and received on a radio channel is determined based on a changeable reference frequency, and information such as voice is modulated and demodulated, and is transmitted and received between a plurality of base stations via the above-described radio channel.
As shown in FIG. 12, this kind of conventional digital portable telephone apparatus is constructed of a common use section 101, a reception section 102, a transmission section 103, a frequency generating section 104, a reference frequency generating section 105, an AFC section 106, a modulation and demodulation section 107, a control section 108, an operation section 109, a display section 110, and a transceiver 111.
A signal (carrier wave signal) on a radio channel, which was received by the common use section 101 via an antenna, is delivered to the reception section 102, and is mixed with a station issue signal, and is replaced by an intermediate frequency signal, and further, is supplied to the modulation and demodulation section 107 and the AFC section 106. The intermediate frequency signal supplied from the reception section 102 is demodulated in the modulation and demodulation section 107, and is output as a voice signal from the transceiver 111 through the control section 108.
On the other hand, the voice that was input to the transceiver 111 passes the control section 108, and is digitally modulated in the modulation and demodulation section 107, and is converted into a signal (carrier wave signal) on a radio channel in the transmission section 103, and after amplified, is supplied to the common use section 101 and is transmitted.
Further, the operation section 109 and the display section 110, which provide convenience for conducting a call, are connected to the control section 108.
A reference frequency signal from the reference frequency generating section 105 is supplied to the frequency generating section 104, and it generates a station issue signal with accuracy equivalent to frequency accuracy of the reference frequency signal by means of a PLL, and supplies it to the reception section 102 and the transmission section 103.
It is required that the reference frequency generating section 105 outputs a frequency that is stable within a certain range. However, since it is also required that the portable telephone apparatus becomes to be small-sized, light and cheap, it is not possible to increase accuracy and stability of an output frequency from the reference frequency generating section 105 so much. Accordingly, a frequency of the station issue signal can be also changed easily, and transmission and reception cannot be sometimes conducted at a desired frequency on the radio channel.
On the other hand, since output frequency accuracy and stability of the reference frequency generating means in each base station of a digital mobile communication system are extremely high, with regard to a carrier wave signal transmitted and received on a radio channel, a frequency deviation from a prescribed frequency can be extremely reduced. In addition, quantities of the deviation are slightly different from each other for every base station. Therefore, on a side of the digital portable telephone apparatus, it is necessary to make a frequency deviation in transmission and reception of the apparatus coincide with a frequency deviation of a carrier wave signal of a base station to be connected, that is to say, a frequency deviation of an intermediate frequency signal corresponding thereto, and AFC (Automatic Frequency Control) is conducted for a reference frequency of the apparatus.
In the AFC control in a prior art, first, the AFC section 106 sends one determined initial control signal to the reference frequency generating section 105, and the reference frequency generating section 105 generates a frequency for a value of the provided initial control signal. The AFC section 106 changes a value of the control signal so as to coincide with a frequency deviation of the intermediate frequency signal supplied from the reception section 102, and controls the reference frequency generating section 105.
However, if the above-mentioned AFC control is conducted in a state where reception electric field condition is not good, there is a case in which a frequency of the reference frequency generating section does not exactly coincide with a frequency deviation of a base station. The reason thereof is because, in condition where a reception electric field is low, due to an effect of phasing, an intermediate frequency signal supplied to the AFC section has a lot of phase noises and frequency counting cannot be exactly conducted, and frequency comparison is mistaken. Similarly, if the AFC control is conducted in a state where reception quality condition is not good, there is a case in which a frequency of the reference frequency generating section does not exactly coincide with a frequency deviation of a base station. The reason thereof is because, in condition where reception quality is bad due to an interference disturbance wave and so forth, the disturbance wave is superimposed on an intermediate frequency signal supplied to the AFC section, and thereby, frequency counting cannot be exactly conducted, and frequency comparison is mistaken.
Although there is means for always operating the AFC control as means for solving these tasks, since a consumption electric current becomes to be large, it is not preferable for a digital portable telephone apparatus in which a battery is used for a power supply.
Also, it is known that control of the reference frequency generating section is significantly influenced by heat. In the portable telephone apparatus, since external environment temperature changes suddenly with movement, and the transmission section generates extreme heat during calling, a temperature changing range becomes to be broad. Accordingly, high stability is required for the reference frequency generating section over a wide range even for a temperature change.
Although, as a method for solving this task, to use a reference frequency generating device is considered, which has high stability over a wide range even for a temperature change, and can conduct voltage control, a frequency generating section that meets both conditions is not general one.
The present invention is made to solve the above-mentioned problems.
Moreover, the objective of the invention is to provide a portable telephone apparatus capable of preventing increase of a consumption electric current without continuously conducting AFC control and keeping communication condition good even though heat influence exists.
The present invention for accomplishing the above-described objective is a portable telephone apparatus characterized in that the apparatus comprises:
reference frequency generating means capable of changing an output frequency for communication with a base station by means of a voltage control signal;
high-accurate reference frequency generating means in which frequency accuracy always meets a prescribed value;
determination means for determining whether or not frequency accuracy of an output signal from the above-described reference frequency generating means meets a predetermined prescribed value; and
selection means for selecting an output signal from the above-described reference frequency generating means in case that a determination result of the above-described determination means meets the above-described prescribed value, and for selecting an output signal from the above-described high-accurate reference frequency generating means in case that a determination result of the above-described determination means does not meet the above-described prescribed value.
In addition, it is preferable that an output signal from the above-described reference frequency generating means, which is used for the above-described determination, is an output signal after an AFC operation of the above-described reference frequency generating means.
In the present invention, with regard to a reference frequency output from the reference frequency generating section means inside the portable telephone, which influences a transmission and reception characteristic, in case that frequency accuracy of the reference frequency does not meet the prescribed value (frequency accuracy within a range in which the portable telephone can conduct transmission and reception) due to a frequency shift of the reference frequency by means of heat, failure of the AFC operation and so forth, it becomes to be possible to stably supply the reference frequency by switching the reference frequency to the output signal from the high-accurate reference frequency generating means.
Accordingly, the present invention has a feature that, even though heat influence exists due to long-time calling and so forth, a transmission and reception characteristic can be kept good.
Also, in the above-described present invention, if a power supply of the above-described high-accurate reference frequency generating means is turned off other than a time period during which an output signal from the above-described high-accurate reference frequency generating means is used for a reference frequency, and the apparatus further comprises power supply controlling means for turning off a power supply of the above-described reference frequency generating means other than a time period during which an output signal that is used for determination is generated in case that an output signal from the above-described high-accurate reference frequency generating means is used for a reference frequency, consumption power can be saved.
The present invention for accomplishing the above-described objective is a portable telephone apparatus characterized in that the apparatus comprises:
reference frequency generating means capable of changing an output frequency for communication with a base station by means of a voltage control signal;
high-accurate reference frequency generating means in which frequency accuracy always meets a prescribed value;
comparison means for comparing an output signal after an AFC operation of the above-described reference frequency generating means with an output signal from the above-described high-accurate reference frequency generating means;
determination means for determining whether or not frequency accuracy of an output signal after an AFC operation of the above-described reference frequency generating means meets a predetermined prescribed value, based on a comparison result of the above-described comparison means;
selection means for selecting an output signal from the above-described reference frequency generating means in case that a determination result of the above-described determination means meets the above-described prescribed value, and for selecting an output signal from the above-described high-accurate reference frequency generating means in case that a determination result of the above-described determination means does not meet the above-described prescribed value; and
power supply controlling means for turning off a power supply of the above-described high-accurate reference frequency generating means in case that an output signal from the above-described high-accurate reference frequency generating means is used for a reference frequency and other than a case in which an output signal from the above-described high-accurate reference frequency generating means is used in the above-described comparison, and for turning off a power supply of the above-described reference frequency generating means in case that an output signal from the above-described high-accurate reference frequency generating means is used for a reference frequency and other than a time period during which an AFC operation is conducted.
Also, in the above-described present invention, the apparatus further comprises:
RSSI measuring means for measuring RSSI based on a reception signal; and
RSSI comparison means for storing a predetermined RSSI threshold value in advance, and comparing the above-described RSSI threshold value with an RSSI measurement value measured by the above-described RSSI measuring means, and
the above-described determination means is constructed so as to conduct determination in case that, with regard to a comparison result of the above-described RSSI comparison means, the above-described RSSI measurement value is smaller than the above-described RSSI threshold value, and an output signal from the above-described reference frequency generating means is used for a reference frequency, and in case that the above-described RSSI measurement value is larger than the above-described RSSI threshold value, and an output signal from the above-described high-accurate reference frequency generating means is used for a reference frequency, and thereby, since the number of comparing the output signal from the above-described reference frequency generating means with the output signal from the above-described high-accurate reference frequency generating means is decreased, consumption power can be further saved.
Also, in the above-described present invention, the apparatus further comprises:
measurement means for measuring reception quality of a reception signal; and
reception quality comparison means for storing predetermined reception quality in advance, and comparing the above-described reception quality with reception quality measured by the above-described measurement means, and
the above-described determination means is constructed so as to conduct determination in case that, with regard to a comparison result of the above-described reception quality comparison means, reception quality measured by the above-described measurement means is worse than the above-described reception quality stored in advance, and an output signal from the above-described reference frequency generating means is used for a reference frequency, and in case that reception quality measured by the above-described measurement means is better than the above-described reception quality stored in advance, and an output signal from the high-accurate reference frequency generating means is used for a reference frequency, and thereby, since the number of comparing the output signal from the above-described reference frequency generating means with the output signal from the above-described high-accurate reference frequency generating means is decreased, consumption power can be further saved.
The present invention for accomplishing the above-described objective is a stably supplying method of a reference frequency in a portable telephone apparatus characterized in that the method comprises steps of:
providing reference frequency generating means capable of changing an output frequency for communication with a base station by means of a voltage control signal, and high-accurate reference frequency generating means in which frequency accuracy always meets a prescribed value;
determining whether or not frequency accuracy of an output signal from the above-described reference frequency generating means meets a predetermined prescribed value; and
selecting an output signal from the above-described reference frequency generating means in case that a result of the above-described determination meets the above-described prescribed value, and for selecting an output signal from the above-described high-accurate reference frequency generating means in case that a determination result of the above-described determination means does not meet the above-described prescribed value.
In addition, it is preferable that an output signal from the above-described reference frequency generating means, which is used for the above-described determination, is an output signal after an AFC operation of the above-described reference frequency generating means.
Also, it is preferable that the method comprises steps of:
turning off a power supply of the above-described high-accurate reference frequency generating means other than a time period during which an output signal from the above-described high-accurate reference frequency generating means is used for a reference frequency; and
turning off a power supply of the above-described reference frequency generating means other than a time period during which an output signal that is used for determination is generated in case that an output signal from the above-described high-accurate reference frequency generating means is used for a reference frequency.
The present invention for accomplishing the above-described objective is a stably supplying method of a reference frequency in a portable telephone apparatus characterized in that the method comprises steps of:
providing reference frequency generating means capable of changing an output frequency for communication with a base station by means of a voltage control signal, and high-accurate reference frequency generating means in which frequency accuracy always meets a prescribed value;
comparing an output signal after an AFC operation of the above-described reference frequency generating means with an output signal from the above-described high-accurate reference frequency generating means;
determining whether or not frequency accuracy of an output signal after an AFC operation of the above-described reference frequency generating means meets a predetermined prescribed value, based on a result of the above-described comparison;
selecting an output signal from the above-described reference frequency generating means in case that a result of the above-described determination meets the above-described prescribed value, and selecting an output signal from the above-described high-accurate reference frequency generating means in case that a determination result of the above-described determination means does not meet the above-described prescribed value;
turning off a power supply of the above-described high-accurate reference frequency generating means in case that an output signal from the above-described high-accurate reference frequency generating means is used for a reference frequency and other than a case in which an output signal from the above-described high-accurate reference frequency generating means is used in the above-described comparison; and
turning off a power supply of the above-described reference frequency generating means in case that an output signal from the above-described high-accurate reference frequency generating means is used for a reference frequency and other than a time period during which an AFC operation is conducted.
Also, in the above-described present invention, it is further preferable that the method further comprises steps of:
measuring RSSI based on a reception signal; and
comparing a predetermined RSSI threshold value stored in advance with the above-described measured RSSI measurement value, and
the above-described step of determining whether or not the above-described predetermined prescribed value is met and steps subsequent to this step are conducted only in case that, with regard to a comparison result of the above-described RSSI, the above-described RSSI measurement value is smaller than the above-described RSSI threshold value, and an output signal from the above-described reference frequency generating means is used for a reference frequency, and in case that the above-described RSSI measurement value is larger than the above-described RSSI threshold value, and an output signal from the high-accurate reference frequency generating means is used for a reference frequency.
Also, in the above-described present invention, it is further preferable that the method further comprises steps of:
measuring reception quality of a reception signal; and
comparing reception quality stored in advance with the above-described measured reception quality, and
the above-described step of determining whether or not the above-described predetermined prescribed value is met and steps subsequent to this step are conducted only in case that, with regard to a comparison result of the above-described reception quality, the above-described measured reception quality is worse than the above-described reception quality stored in advance, and an output signal from the above-described reference frequency generating means is used for a reference frequency, and in case that the above-described measured reception quality is better than the above-described reception quality stored in advance, and an output signal from the high-accurate reference frequency generating means is used for a reference frequency.